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Now showing items 113 - 128 of 71381

  • Energy method of M. O. Korpusov and A. G. Sveshnikov

    Korpusov, Maxim Olegovich   Ovchinnikov, Alexey Vital'evich   Sveshnikov, Alexey Georgievich   Yushkov, Egor Vladislavovich  

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  • A&G Volume 58 Issue 2, Full Issue

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  • Notes for A&G authors

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  • Emergent Computation: A Festschrift for Selim G. Akl

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  • A&G Volume 58 Issue 6, Full Issue

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  • A&G Volume 58 Issue 4, Full Issue

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  • A&G Volume 58 Issue 5, Full Issue

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  • A hybrid method for performance analysis of G/G/m queueing networks

    Rabta   Boualem  

    Open queueing networks are useful for the performance analysis of numerous real systems. Since exact results exist only for a limited class of networks, decomposition methods have been extensively used for approximate analysis of general networks. This procedure is based on several approximation steps. Successive approximations made in this approach can lead to a considerable error in the output. In particular, there are no general accurate formulas for computing the mean waiting time and the inter-departure variance in general multiple-server queues. This causes the results from decomposition methods when applied to G/G/m queueing networks to be very approximative and to significantly deviate from actual performance values. We suggest substituting some approximate formulae by low-cost simulation estimates in order to obtain more accurate results when benefiting from the speed of an analytical method. Numerical experiments are presented to show that the proposed approach provides improved performance. (C) 2013 IMACS. Published by Elsevier B.V. All rights reserved.
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  • A&G Volume 58 Issue 2, Full Issue

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  • Elongation factor G initiates translocation through a power stroke

    Chen, Chunlai; Cui, Xiaonan; Beausang, John F.; Zhang, Haibo; Farrell, Ian; Cooperman, Barry S.; Goldman, Yale E.  

    During the translocation step of prokaryotic protein synthesis, elongation factor G (EF-G), a guanosine triphosphatase (GTPase), binds to the ribosomal PRE-translocation (PRE) complex and facilitates movement of transfer RNAs (tRNAs) and messenger RNA (mRNA) by one codon. Energy liberated by EF-G's GTPase activity is necessary for EF-G to catalyze rapid and precise translocation. Whether this energy is used mainly to drive movements of the tRNAs and mRNA or to foster EF-G dissociation from the ribosome after translocation has been a long-lasting debate. Free EF-G, not bound to the ribosome, adopts quite different structures in its GTP and GDP forms. Structures of EF-G on the ribosome have been visualized at various intermediate steps along the translocation pathway, using antibiotics and nonhydolyzable GTP analogs to block translocation and to prolong the dwell time of EF-G on the ribosome. However, the structural dynamics of EF-G bound to the ribosome have not yet been described during normal, uninhibited translocation. Here, we report the rotational motions of EF-G domains during normal translocation detected by single-molecule polarized total internal reflection fluorescence (polTIRF) microscopy. Our study shows that EF-G has a small (similar to 10 degrees) global rotational motion relative to the ribosome after GTP hydrolysis that exerts a force to unlock the ribosome. This is followed by a larger rotation within domain III of EF-G before its dissociation from the ribosome.
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  • Secretory immunoglobulin A and immunoglobulin G in horse saliva

    Anna-Karin E. Palm   Ove Wattle   Torbjörn Lundström   Eva Wattrang  

    Highlights • Reagents for horse IgA and secretory IgA were characterised. • Concentrations of secretory IgA and IgG in saliva from normal horses were recorded. • Local production of IgG in horse saliva was indicated. Abstract This study aimed to increase the knowledge on salivary antibodies in the horse since these constitute an important part of the immune defence of the oral cavity. For that purpose assays to detect horse immunoglobulin A (IgA) including secretory IgA (SIgA) were set up and the molecular weights of different components of the horse IgA system were estimated. Moreover, samples from 51 clinically healthy horses were tested for total SIgA and IgG amounts in saliva and relative IgG3/5 (IgG(T)) and IgG4/7 (IgGb) content were tested in serum and saliva. Results showed a mean concentration of 74 μg SIgA/ml horse saliva and that there was a large inter-individual variation in salivary SIgA concentration. For total IgG the mean concentration was approx. 5 times lower than that of SIgA, i.e. 20 μg IgG/ml saliva and the inter-individual variation was lower than that observed for SIgA. The saliva–serum ratio for IgG isotypes IgG3/5 and IgG4/7 was also assessed in the sampled horses and this analysis showed that the saliva–serum ratio of IgG4/7 was in general approximately 4 times higher than that of IgG3/5. The large inter-individual variation in salivary SIgA levels observed for the normal healthy horses in the present study emphasises the need for a large number of observations when studying this parameter especially in a clinical setting. Moreover, our results also indicated that some of the salivary IgG does not originate from serum but may be produced locally. Thus, these results provide novel insight, and a base for further research, into salivary antibody responses of horses.
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  • IL-2-330T/G polymorphism and cancer risk: a meta-analysis

    Zhao, Hongyu   Wang, Rui  

    Purpose: Some studies have investigated the association of IL-2 -330T/G (rs2069762) polymorphism with cancer risk, but the previous results were conflicting and had relatively low statistical power. Thus, we performed a meta-analysis to derive a more precise estimation of the association between IL-2 -330T/G polymorphism and cancer risk. Methods: A literature search was performed systematically using electronic databases. The odds ratio (OR) with 95% confidence interval (CI) was used to estimate the pooled effect. Results: A total of ten studies including 3,060 cases and 3,435 controls were involved in this meta-analysis. The results indicated that IL-2 -330T/G polymorphism was significantly associated with cancer risk ([OR =3D 2.03, 95% CI =3D 1.40-2.95] for GG vs TT; [OR =3D 1.37, 95% CI =3D 1.11-1.69] for GT vs TT; [OR =3D 1.46, 95% CI =3D 1.18-1.81] for [GG + GT] vs TT; [OR =3D 1.66, 95% CI =3D 1.24-2.23] for GG vs [GT + TT]; and [OR =3D 1.35, 95% CI =3D 1.16-1.57] for G vs T). In the subgroup analysis according to cancer type, significant association was found in lymphoma ([OR =3D 1.46, 95% CI =3D 1.11-1.91] for GT vs TT; [OR =3D 1.58, 95% CI =3D 1.22-2.05] for [GG + GT] vs TT; [OR =3D 1.84, 95% CI =3D 1.22-2.77] for GG vs [GT + TT]) and other cancers, but not in gastric cancer. In the subgroup analysis by ethnicity, the significant risk was found among Asians, but not among Europeans. Conclusion: This meta-analysis suggests that IL-2 -330T/G polymorphism has an increased risk of cancer in Asians. However, further detailed studies are still required to confirm our findings.
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  • A measurement of G with a cryogenic torsion pendulum

    Newman, Riley   Bantel, Michael   Berg, Eric   Cross, William  

    A measurement of Newton's gravitational constant G has been made with a cryogenic torsion pendulum operating below 4 K in a dynamic mode in which G is determined from the change in torsional period when a field source mass is moved between two orientations. The source mass was a pair of copper rings that produced an extremely uniform gravitational field gradient, whereas the pendulum was a thin fused silica plate, a combination that minimized the measurement's sensitivity to error in pendulum placement. The measurement was made using an as-drawn CuBe torsion fibre, a heat-treated CuBe fibre, and an as-drawn Al5056 fibre. The pendulum operated with a set of different large torsional amplitudes. The three fibres yielded high Q-values: 82 000, 120 000 and 164 000, minimizing experimental bias from fibre anelasticity. G-values found with the three fibres are, respectively: {6.67435(10), 6.67408(15), 6.67455(13)} x 10(-11) m(3) kg(-1) s(-2), with corresponding uncertainties 14, 22 and 20 ppm. Relative to the CODATA2010 G-value, these are higher by 77, 37 and 107 ppm, respectively. The unweighted average of the three G-values, with the unweighted average of their uncertainties, is 6.67433(13) x 10(-11) m(3) kg(-1) s(-2) (19 ppm).
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  • Identification of an RNase that preferentially cleaves A/G nucleotides

    Xie, Jumin   Chen, Zhen   Zhang, Xueyan   Chen, Honghe   Guan, Wuxiang  

    Ribonucleases play an important role in the RNA metabolism which is critical for the localization, stability and function of mature RNA transcripts. More and more ribonucleases were discovered in recent years with the progress of technology. In the present study, we found that the uncharacterized C19orf43, a novel interacting protein of human telomerase RNA (hTR), digested T7 transcribed RNA, total cellular RNA and RNA oligos but not DNA. Thus we named this new RNase as hTRIR (human telomerase RNA interacting RNase). Genetic analysis showed that hTRIR is conserved among eukaryotic species and widely expressed in different cell lines. The RNase activity of hTRIR works in a broad temperature and pH range while divalent cations are not required. The conserved C-terminus of C19orf43 is necessary for its activity. Finally, we found that hTRIR cleaves all four unpaired RNA nucleotides from 5' end or 3' end with higher efficiency for purine bases, which suggested that hTRIR is an exoribonuclease. Taken together, our study showed the first evidence of the novel function of hTRIR in vitro, which provides clue to study the regulatory mechanism of hTR homeostasis in vivo.
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  • Novel mitochondrial tRNAArg 10461A>G mutation in a pedigree with obesity

    Wang, Jin-Ling   Ji, Yan-Chun   Fu, Jun-Fen  

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  • Dental treatment of a patient with Opitz G/BBB syndrome

    Giovani, Elcio Magdalena   Tarquinio Marinho, Kelly Cristine   Andia-Merlin, Ruth  

    Opitz G/BBB syndrome is a genetic condition characterized by several abnormalities along the midline of the body, such as hypertelorism, craniofacial deformities, and dysphagia. This study reports the clinical features of Optiz syndrome and its importance in the knowledge of patients who are developmentally challenged as a whole, in order to establish adequate dental treatment for a certain clinical case. A 19-year-old patient visited the Paulista University for a dental treatment. The extraoral examination revealed ocular hypertelorism (wide-spaced eyes), oblique eyelids, epicanthus, low-set cart, and intellectual disability. During the intraoral examination, large caries lesions were observed surrounding the braces of the fixed orthodontic appliance and poor oral hygiene. Preventive and restorative treatments were carried out. It was concluded that the knowledge of patients with special needs as a whole is mandatory for an adequate dental treatment. This is a case report that highlights the importance of dentist and interdisciplinary care attendance for all patient systems, the examination and analyses should not be restricted to the oral cavity.
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